Suppose that an alpha particle of 3.20 MeV approaches head-on a lead nucleus (Z = 82). Assuming that the lead nucleus remains at rest and the alpha particle momentarily comes to rest and reverses its direction at a distance much more than the radius of the lead nucleus, the distance of its closest approach is:
1
24.6 fm
2
36.9 fm
3
59.2 fm
4
73.8 fm